What is the best underlay for a floating wood floor?

There are several different types of wood floor and floating floors are the most common. Once you have chosen the floor type that best meets your needs, it's time to decide what underlay to install.
Floating wood floors are not installed directly onto the floor of the room. Instead, they sit on top of an underlay, which makes the strips easier to install and helps insulate your home as much as possible.
All floating wood floors require an underlay to help protect them from general wear and tear, but there are several different types to choose from; each with their pros and cons.
So what type of underlay is most suitable for a floating wood floor?

How thick should the underlay be to install a floating wood floor?

In contrast with glue-down wood floors, floating floors need to be installed on top of an underlay. Before learning how to lay the sheets, here's why an underlay is so important.

The underlay helps even out the floor underneath the floating wood strips

Floating wood floors are composed of many strips or boards that need to be carefully assembled. In the case of home renovation, the floor of the room is often not entirely even and may have bumps and/or dents.
These small differences in height can be adjusted by installing an underlay, which can even out the floor below the floating strips by as much as 4 or 5 mm.
The underlay also makes it easier to install the wood floor strips and click them into position. It ensures that they have a stable structure on which to rest.

How thick should the underlay be to install a floating wood floor?

Sometimes, people assume that any thick or padded material (such as a rug) will make a good wood floor underlay. In reality, an underlay that is too thick will create too much space between the different parts of the floating floor, putting strain on the points where the strips meet. To put it simply, an overly thick underlay makes the wood floor too flexible and therefore weaker.
That's why you should choose the underlay for your floating floor with care. In general, a thickness of several millimetres is sufficient.

Choosing an underlay with the right level of insulation

Thermal insulation should be your main priority when choosing a floating wood floor underlay.

Thermal insulation is the most important type of insulation. It's essential to choose an underlay that doesn't retain or transfer heat from the wood floor. A good underlay should improve the comfort of your home and help you save money on your energy bill.
If you have underfloor heating, it's also important to make sure your chosen underlay is compatible with this kind of floor.

The acoustic and soundproofing properties of a wood floor underlay

People who have noisy neighbours living upstairs will be able to vouch for the fact that sound and vibrations are easily transmitted from one floor to another. Wood floor underlays are designed to reduce noise disturbance. This is what's called soundproofing and acoustic insulation.
Soundproofing refers to the prevention of noise transmission from the inside to the outside of a property.
Acoustic insulation is the reduction of echoes and resonance and the prevention of noise transmission inside a property.
In other words, a floating floor underlay is designed to reduce the transmission of impacts (footsteps, falling objects, washing machine vibrations) between the wood and the floor. Your insulation requirements will differ depending on your property, the neighbouring properties and the room where your wood floor is installed.

Choosing a suitable floating wood floor underlay for your chosen room

Underlay is designed to protect the wood of your floating floor as much as possible.

Moisture can vary considerably from one room to the next, depending on each one's location within the property, the amount of sunlight received and how well ventilated the space is. Any temperature fluctuations and the transfer of heat (or lack of it) between the wood and the floor can lead to problems with moisture.

Do I need a vapour barrier for my floating floor underlay?

Concrete is a porous material so any floors made of concrete are susceptible to mould. Once moisture seeps into the floors, it can easily make its way into the wood strips if they are not sufficiently protected.
Aside from the annoyance caused by having residual moisture in the room, it can also cause the wood floor to rapidly deteriorate.
If you have a concrete floor, it's important to lay a vapour barrier. This plastic sheet insulates the rest of the floor from moisture and makes it practically watertight.
However, depending on where you install your floating wood floor, a vapour barrier may prove more of a hindrance than a help. Certain natural materials like wood need to 'breathe'. The same applies to engineered and laminated wood. A vapour barrier traps moisture;,causing wood floors to degrade faster than they normally would. In this case, polyethylene foam makes a suitable alternative to a vapour barrier as it enables the floor to breathe.
There is one exception to the rule: if the wood floor is installed in a very humid space like a bathroom, laying a vapour barrier is a smart move.

The different types of floating wood floor underlays

Polyethylene (PE) foam underlay – the most economic underlay

The most common type of underlay, polyethylene foam is cheap, easy to install and comes in ready-to-use rolls. It is thinner than other types of underlay and therefore less insulating:

  • PE foam can even out bumps or dents of up to 2 mm
  • It offers good thermal insulation
  • It provides sufficient acoustic insulation
  • It is not watertight and therefore not recommended for wood floors that are exposed to moisture

Extruded polystyrene (XPS) underlay – the most comprehensive underlay

XPS underlay comes in ready-to-use slabs or rolls and has several benefits.

  • It varies in thickness from 1-mm to 10-mm thick, making it suitable for any kind of floorboard set-up.
  • It's the best material for evening out the floor (for bumps and dents up to 4 or 5 mm)
  • It has excellent soundproofing qualities
  • It offers the best thermal insulation
  • It is resistant to moisture
  • It stands up well to any knocks
  • It is very vulnerable to fire damage

Cork underlay – the most eco-friendly underlay

Cork underlay comes in ready-to-use slabs or rolls and makes a good sustainable alternative to non-natural underlays.

  • Its thickness varies from 2 to 8 mm, making it highly adaptable
  • It can only even out small bumps and dents in the floor (up to 0.5 mm)
  • It offers the best soundproofing
  • It offers the best acoustic insulation
  • It stands up well to any knocks
  • It is environmentally friendly
  • It is not watertight and therefore needs to be laid on top of an insulating underlay if the wood floor will be exposed to any moisture

Natural wood fibre underlay – the most environmentally responsible underlay

Natural wood fibre underlay is an eco-friendly alternative to non-natural underlays and comes in ready-to-use slabs. It is versatile as well as recyclable.

  • It can be used to even out bumps and dents of up to 3 mm
  • It has great soundproofing qualities
  • It offers very good thermal insulation
  • It offers adequate resistance to moisture
  • It is environmentally friendly and recyclable

What is the most suitable underlay for a floating wood floor?

When choosing an underlay for your floating wood floor, it's important to consider the two weaknesses inherent to this kind of flooring.
The first is the risk of moisture seeping out through the floor, especially if it is made of concrete. It is therefore important to choose a moisture-resistant underlay or a vapour barrier.
The second is floating floors' increased propensity to amplify sound compared to other types of wood floor. Underlays should therefore be soundproof and offer excellent acoustic insulation.
You may also want to consider other factors, such as sustainability. If you have any questions, the Panaget team is always available. Get in touch with our advisers to find out more.